Development of permanent implantable catheter systems, temporary diagnostic and therapeutic catheters and implantable devices has resulted in life-saving benefits, and has greatly improved the quality of life of patients across virtually the entire spectrum of medical treatment. However, the proper placement and positioning of invasive catheters, tubes and devices is critical to their effective use. For example, it is typically desirable to apply medications, nutrients or diagnostic probes to a specific location in the body using catheters or tubes.
Positioning of these medical devices is usually done without benefit of any type of real-time visual guidance. Often catheters and catheter-type devices must be steered through a tortuous path and positioned at a site some distance from the proximal insertion point in the patient. The location of the distal tip of this medical device is unknown until some confirmatory study is performed, such as an x-ray. In cases where positioning is particularly critical, x-rays can be used to locate and position the inserted implant, medical device, catheter or tube. Often, following the confirmatory study, the position of the medical device has to be adjusted or may need to be reinserted to achieve proper position of the tip or other critical location(s) on the device.
For example, when an endotracheal tube is used to provide a patient with a mixture of oxygen and air, it is essential that the tube be correctly placed. If the endotracheal tube is in an incorrect position, possibly either too high or too low, either one lung will not be ventilated at all or if the tube is above the vocal cords, neither lung will be ventilated. Radiographs are commonly taken, sometimes at frequent intervals, to establish that an endotracheal tube has been and remains properly located. Similarly, when an orogastric tube is placed into a patient, radiographs are routinely taken to ascertain that the tube ends in the patient's stomach, and not in the duodenum or the esophagus. The same principles apply to the placement of arterial or venous catheters, wherein placement is critical with regard to established reference points.
Some medical devices are subject to movement after insertion due to changes in patient position, weakening of the device's securement to the body, rapid infusion of fluids, or removal of guidewires or introducers used during the device insertion process. This necessitates regular, often at least daily, surveillance of the medical device position with x-rays.
Positioning techniques using x-rays have several shortcomings. Often multiple x-rays are required to locate or confirm the position of an inserted device, subjecting the patient to undesirable levels of ionizing radiation. This problem increases when handling or movement of the patient necessitates periodic rechecking of tube placement. Additionally, x-ray equipment can be large and cumbersome to use, and often is not readily available at the patient bedside when a catheter must be inserted, or placement of an indwelling catheter verified or readjusted. As a result, considerable time and effort are involved in taking repeat radiographs, adding significantly to patient care costs and to delays in optimal therapy. Alternative attempts to properly place the device without the aid of any real-time visual placement tool can make proper positioning of the device a difficult and time-consuming task.
U.S. Pat. No. 4,567,882 (Heller et al.) provides a method for locating the tip of an endotracheal tube inserted into a patient's trachea to provide an airway, wherein the endotracheal tube that is inserted through the patient's mouth or nose includes a means for emitting and laterally projecting a beam of high-intensity visible light (wavelength 4000 to 7700 Å) from a point on the wall of the tube immediately adjacent to the distal end. Consequently, position of the tip of the endotracheal tube can be externally and visually observed as a high intensity visual light, projected laterally through the body to the outside of the patient. However, the heat generated by such a high intensity light over time can cause burns to the delicate tissues lining the patient's airway. This is recognized in U.S. Pat. No. 5,007,408 (Ieoka), which regulates the light in a similar system by using color-separating filters. The light is pulsed for predetermined time intervals through an iris-controlled circuit to reduce the heat that is generated, thereby keeping the temperature slightly below tissue damaging levels. U.S. Pat. No. 5,005,573 (Buchanan) provides a light emitting endotracheal tube connected to, and controlled by, an external oximeter.
Light emitting systems are often used to detect irregularities in a duct, vessel, organ or the like. U.S. Pat. No. 4,248,214 (Hannal et al.) provides an illuminated urethral catheter to assist a surgeon in locating the junction of the bladder and the urethra to permit the proper performance of the Marshall-Marchetti-Kranz procedure. U.S. Pat. No. 4,782,819 (Adair) is representative of many patents using catheters for illuminating organs for internal inspection. For example, U.S. Pat. No. 5,947,958 (Woodward et al.) provides a system for the illumination of internal organs of a patient after insertion through, for example, the peritoneal wall. In that case, the light is provided for either imaging of the tissue surface or for delivering light for use in photodynamic therapy. However, such devices are not used for catheter placement, and are not the subject of the present invention.
In a conventional endoscope an illuminating light emitted from a light source outside the body is introduced into the body cavity through a light guide, which is inserted through a tube. The light is radiated onto tissue within the body cavity. In order to observe the tissue surface within the body cavity, the light, which is reflected from the surface of the tissue, is received and observed with the naked eye using an eyepiece, or is imaged by a television camera or the like. However, with conventional endoscopes the character of the viewed tissue, such as the venous circulation below the mucous membrane of the stomach or the minute structure of the venous system, cannot be seen. As a result, U.S. Pat. No. 4,898,175 (Noguchi) provides an imaging device in which a constant illuminating light is shined onto the tissue being observed through a catheter-type device inserted into the patient's body, permitting the interior of the tissue to be observed using a viewing device that images the light emitted to the outside of the body and processed by a signal processing device. The imaging of the '175 patent utilizes a solid state imaging device, wherein the illuminating light is sequentially switched among a variety of colors, or a single plate system, wherein a color filter is fitted to the front surface of the solid state imaging device to obtain a color picture image. However, the image is designed only to permit visualization of the tissue onto which the light is projected. It is not used as an optical guidance means for placing a catheter or scope quickly, easily and precisely within the patient's body.
U.S. Pat. Nos. 5,423,321; 5,517,997; 5,879,306; 5,910,816; 6,516,216; 6,597,941; 6,685,666 (Fontenot) provide multiple light guiding fibers of different lengths that are inserted into internal organs or vessels during surgery to reduce the danger of erroneously cutting into a passage or organ during surgery. The Fontenot catheter comprises an infrared-emitting flexible, polymeric, preferably round light guide encased in a flexible essentially infrared-transparent outer covering, such that infrared light is circumferentially emitted over the entire length of the duct, passage, etc of the patient, which permits the length of the passage to be viewed by the surgeon via an infrared photodetector. By placing a single emitter or line of emitters in the structure, the Fontenot patents operate to create a background of light against which the proximity of surgical instruments to organs or passages is determined by measuring intensity of light emitted, but the patents fail to provide or suggest precise and accurate information with regard to placement of the emitter in the patient.
U.S. Pat. No. 5,906,579 (Vander Salm et al.) and U.S. Pat. No. 6,113,588 (Duhaylongsod et al.) similarly describe methods for visualizing balloon catheters through the vessel wall under surgical conditions, specifically during cardiothoracic surgery. In these devices, the optical fiber is an independent entity, preferably inserted through one lumen of a multi-lumen catheter.
U.S. Pat. No. 5,540,691 (Elstrom et al.) provides a detection system consisting of a light source which is passed down the center of the intramedullary rod and a video system, sensitive to infrared light, which captures an image of the light transmitted through the transverse hole in the rod. The light simply shines out toward the surgeon who attempts to line up the drill by centering it on an area of light coming out of the hole. The infrared light is visualized using either a video system or night vision goggles to determine when the light intensity is centered around the drill.
U.S. Pat. No. 6,081,741 (Hollis) uses an array of inexpensive sensor elements to determine the center of an emitter that transmits light at a predetermined wavelength. For alignment purposes, the '741 patent provides the relative direction and relative amount of movement to rapidly achieve accurate alignment or orientation with regard to the emitted light spreading from the point source.
A series of related published patent applications 2002/0115922, 2003/0187360 and 2004/0019280 (Waner et al.) provide infrared monitoring of an intraluminal indwelling catheter, wherein optical properties are varied to form patterns to distinguish the light emitting catheter from adjacent anatomical structures.
Several patents, e.g., U.S. Pat. No. 4,784,128, use infrared sensors internally in the patient to locate heat generating body tissue, such as cancers. U.S. Pat. No. 4,821,731 uses a sound generating catheter to image internal features of the body.
Accordingly, as indicated above, prior efforts in this field have related primarily to protecting, managing, viewing, or treating parts of the patient's body. However, prior to the present invention, none of the prior art devices have been adapted to quickly, easily and precisely guide a catheter or other invasive delivery tube or device to an exact location within the patient. A need has existed, therefore, for a system and method to reliably locate and position invasive devices that overcomes these shortcomings without the requirement for x-rays or other cumbersome devices.